[clang] [CIR] Handle NullStmt (PR #134889)

[Erich Keane via cfe-commits]

================
@@ -57,6 +57,7 @@ mlir::LogicalResult CIRGenFunction::emitStmt(const Stmt *s,
 
   switch (s->getStmtClass()) {
   case Stmt::BreakStmtClass:
+  case Stmt::NullStmtClass:
----------------
erichkeane wrote:

I'm about 99.9% sure that there is no code that can result in it, barring some error in the compiler.  It is the 'class' of `Stmt`, which isn't `virtual`, but is effectively abstract (other than by language rule).

https://github.com/llvm/llvm-project/pull/134889